The present invention generally relates to a lumber transfer system. More particularly, it concerns a lumber transfer system for transferring lumber pieces from a lower conveyor to an upper conveyor, or from the upper conveyor to the lower conveyor. The present invention also relates to a quality control station for lumber pieces including the above-mentioned transfer system, which is useful in wood planning mills.
The use of lumber transfer systems in a quality control station is already known in the prior art. These lumber transfer systems are generally used to transfer the lumber pieces conveyed on a main conveyor onto an upper conveyor on which the quality control of the board may take place. Lumber transfer systems are also used to transfer the lumber pieces from the upper conveyor back to the main conveyor.
Different quality control stations using lumber transfer system exist in the field for the purpose of classifying lumber pieces. One known type of quality control station is shown in FIG. 1. This station is mounted above a main conveyor (109) and has a pivoting ramp (101) which engages a lumber piece (1) conveyed on the main conveyor (109) and lifts it up until it slides off to a turning piece assembly (105). The turning piece assembly (105) flips the lumber piece (1) upside down onto a short conveyor (108) disposed beside the turning piece assembly (105) and above the main conveyor (109). The short conveyor (108) has lugs (106) for carrying a lumber piece (1) transversally. At the end of the short conveyor (108), the lumber piece (1) slides onto an exit ramp (107) and returns to the main conveyor (109). A quality control person is positioned in front of the station, and evaluates one side of the lumber piece (1) when it lies on the turning piece assembly (105) and the other side of the lumber piece (1) when it lies on the short conveyor (108) so as to classify the lumber piece (1) into its appropriate category of quality.
Another type of quality control station is shown in FIGS. 2 and 3. This station is mounted above a main conveyor (201) and has a set of aligned pivotable ramps (203) which are pivoted up timely to direct a lumber piece (1) conveyed onto the main conveyor (201) toward a belt strap (204) oriented upwardly to bring the lumber piece (1) to an upper conveyor (206). Aligned lugs (202) of the main conveyor (201) push the lumber piece (1) onto the pivotable ramps (203), which direct it upwardly on the belt strap (204). Turning piece assemblies (207) are mounted onto the short conveyor (206) and turn the lumber piece (1) which is conveyed on the short conveyor (206), upside down. Another belt strap (208) disposed at the end of the short conveyor (206) receives the lumber piece (1) and carries it downwards to another set of pivotable ramps (209) which direct the lumber piece (1) to the main conveyor (201).
A drawback of the quality control station shown in FIGS. 2 and 3 lies in the belt straps (204) at the entry, since one end of a lumber piece (1) can slide back and therefore, the piece (1) would enter obliquely on the short conveyor (206), and jam the station.
An object of the present invention is to propose a lumber transfer system designed to reduce the possibilities of misalignment of the lumber pieces during their transfer from either the main conveyor to the upper conveyor or from the upper conveyor back to the main conveyor.
In accordance with the present invention, that object is achieved with a first lumber transfer system for transferring lumber pieces conveyed on a lower conveyor to an upper conveyor disposed above the lower conveyor, the lumber pieces being conveyed transversally with reference to their length, the lumber transfer system comprising:
a controllable loading ramp having a receiving end and an exit end and being movable therebetween:
i) a loading position to direct the lumber pieces from the lower conveyor toward the upper conveyor and where the receiving end is set to receive the lumber pieces from the lower conveyor and the exit end is set to transfer said lumber pieces to a loading end of the upper conveyor; and
ii) a standby position where the ramp is set out of the way of the lumber pieces conveyed on the lower conveyor;
a controllable pushing means for engaging and pushing a lumber piece conveyed on the lower conveyor onto and along the ramp when the ramp is in the loading position until the lumber reaches the loading end of the upper conveyor; and
a controlling means for controlling and synchronizing the pushing means and the movement of the loading ramp.
Preferably, the controllable pushing means comprises at least one wheel mounted on a rotating shaft extending transversally above the lower conveyor, the wheel extending in a plane parallel to the lower and upper conveyors and including at least one arm projecting radially therefrom to engage and push a lumber piece onto and along the loading ramp; and
driving means for driving the shaft into rotation; and wherein the controlling means further control the driving means.
The invention is also directed to a second lumber transfer system for transferring lumber pieces conveyed on an upper conveyor to a lower conveyor disposed below the upper conveyor, the lumber pieces being conveyed transversally with reference to their length, the lumber transfer system comprising:
a sliding ramp to guide a lumber piece leaving an unloading end of the upper conveyor toward the lower conveyor, the sliding ramp having a receiving end in communication with the unloading end of the upper conveyor to receive the lumber piece coming from the upper conveyor and an exit end settable to deliver the lumber piece on the lower conveyor; and
a controllable supporting means for controlling the fall of a lumber piece sliding by gravity along the sliding ramp until it reaches the lower conveyor; and
a controlling means for controlling the supporting means.
Preferably, the controllable supporting means comprises at least one wheel mounted on a rotating shaft extending transversally above the lower conveyor, the wheel extending in a plane parallel to the upper and lower conveyors and including at least one arm projecting radially therefrom to support a lumber piece sliding on the sliding ramp; and
driving means for driving the shaft into rotation; and wherein the controlling means for controlling the supporting means further control the driving means.
The present invention further proposes a quality control station for lumber pieces conveyed in parallel on a main conveyor and transversally with reference to their length; the quality control station comprising:
a first upper conveyor disposed above the main conveyor and having a loading end and an unloading end,
a first turning means mounted on the first upper conveyor for turning upside down a lumber piece conveyed thereon;
a second upper conveyor disposed above the main conveyor downstream from the first upper conveyor; the second upper conveyor having a loading end and an unloading end,
a second turning means mounted on the second upper conveyor for turning upside down a lumber piece conveyed thereon;
a first lumber transfer system as defined above for transferring the lumber pieces conveyed on the main conveyor to the first upper conveyor;
a second lumber transfer system as defined above for transferring the lumber pieces conveyed on the second upper conveyor back to the main conveyor; and
a third lumber transfer system for transferring lumber pieces conveyed on the first upper conveyor back to the main conveyor and also for transferring lumber pieces conveyed on the main conveyor to the second upper conveyor.
As it can be appreciated, the present invention provides a better control of the lumber pieces transferred from a conveyor to an other conveyor located above or below. More specifically, thanks to the pushing means or the supporting means, the risk of misalignment of the lumber pieces being transferred is greatly reduced.
The invention and its advantages will be better understood upon reading the non-restrictive description of a preferred embodiment of the present invention. This description is given with reference to the appended drawings.